Fluid flow meters are well known in the prior art and they exist in various forms and constructions. The prior art flow meters commonly have a piston which is displaced in accordance with the rate of flow through the meter, and it is old to have the housing of a transparent material so that the position of the piston can be observed and thus the rate of flow determined. Examples of such prior art are found in British Pat. No. 928,319 and in U.S. Pat. Nos. 2,311,181 and 2,370,634 and 2,439,614, and 2,655,041 and 3,196,673. However, those prior art patents are of structures significantly different from the one disclosed herein, in that the prior art structures have their so-called piston members floating, rather than spring-urged and operating over a fixed cone, as in the present invention.
The prior art is also aware of flow meters which utilize a remote type of indicator, such as a pointer and dial or the like, and U.S. Pat. Nos. 1,499,839 and 2,325,884 and 2,574,866 and 3,398,305 show that type of flow meter structure and it differs from the present invention which utilizes a spring-urged piston which can be seen through a transparent housing for determining the rate of flow.
Still another group of prior art patents is U.S. Pat. Nos. 2,638,582 and 3,218,853 and 3,554,031 shows meters or valves which have pistons slidable in a conical housing, but they do not relate the piston to a transparent housing through which the position of the piston can be seen and thus the rate of flow determined.
All of the aforementioned prior art patents differ from the present invention in that the present invention has the spring-urged piston slidable in a cylindrical housing of transparent material and there are fins on the upstream side of the flow in the housing so that the flow can become steady and laminar and thus create a steady force on the piston for the desired accurate reading. Further, the present invention has an adjustable seat for the spring which urges the piston, and thus the spring can be put under proper tension and therefore it is in the nature of calibrating the spring for the particular meter installation and characteristics of that individual spring, and thus, again, an accurate flow rate reading can be obtained by this means which differs from the prior art. Still further, the present invention differs from the aforesaid prior art in that it is made of only a minimum number of pieces and thus there is no requirement for elaborate interfitting of parts and there is no requirement for extensive assembly proceedings as there is with the prior art structures such as those mentioned above. Still another prior art patent is U.S. Pat. No. 3,805,611 which employs a spring-urged movable piston operating on a conical member and having a cylindrical housing interior and with the position of the piston itself indicating the rate of flow through the meter. However, for the reasons mentioned in this paragraph, the present invention also distinguishes over U.S. Pat. No. 3,805,611, that is, the present invention has the flow fins, the adjustable spring seat, and the minimal number of parts. That prior art flow meter has twenty-two pieces compared to five pieces required for the present flow meter, for example. Therefore, the present meter is less subject to failure of parts, and there is significantly less requirement for fitting the parts one to another and thus the meter can be an accurate meter with less manufacturing expense and attention, and, significantly, the present meter does not rely upon the use of a magnet, as with U.S. Pat. No. 3,805,611 for the reading of the position of the piston within the housing.
There are other objects and advantages, and those will become apparent upon a reading of the following description in light of the accompanying drawings.